Recent advances in our understanding of the physiology and biochemistry of the arthropods that transmit disease have been gratifying, such that a body of information detailing the interface between vector and host has begun to emerge. Particularly fruitful have been efforts describing developmental processes of vectors specifically stimulated by contact with their hosts. These include vitellogenesis, oogenesis, pheromone production, digestion, salivation, mating, sperm activation and development of pathogens. Such diverse arthropods as mosquitoes and ticks, tsetse flies and bugs, sandflies and fleas and vectors of plant as well as animal infections have been the subjects of these studies. The similarity of the stimuli that initiate these processes provides the focus of the proposed symposium. We anticipate that basic concepts relating to disease transmission will arise from this attempt to describe how vector arthropods respond to their hosts. The proposed symposium serves as an initial attempt to promote communication between the scientists addressing this range of topics. Sufficient time for extensive communication will be provided by the extended format and the unitary focus of discussion. Support is thus requested for a 4-day international symposium on "Host Regulated Developmental Mechanisms in Vector Arthropods" that will convene in February 1986. Scientists who work on vector arthropods have been contacted and enthusiastic positive responses from over 70 researchers have been received. Responses also determined the time of the year and decision to publish a Proceedings of the symposium.